The invention relates to speech coding devices and methods, such as for speech recognition systems.
In speech recognition systems, it has been known to model speech units (for example words, subwords, or word sequences) as producing either (1) acoustic feature vectors representing the values of the features of an utterance, or (2) acoustic labels representing discrete sets of acoustic feature vectors. Models producing acoustic feature vectors are sometimes referred to as continuous parameter models. On the other hand, models producing acoustic labels are sometimes referred to as discrete parameter models. While continuous parameter models are capable of representing more acoustic information than discrete parameter models (and are therefore capable of more accurately representing speech units), continuous parameter models are also more difficult to accurately build than discrete parameter models.